The word "porifera" comes from the Latin porus, or pore, plus ferre, to bear.
With
neither true tissues nor organs, sponges are the most
primitive of multicellular animals.
Characteristics (1) Body structure permeated with flagella-lined openings through which water is swept and food particles and oxygen extracted; (2) stationary as adults.
Size From 1/4 inch to six feet.
Habitat Marine, although one family does live in fresh water.
Other Characteristics Internal skeleton with varying structures made of calcareous and siliceous needles.
Class
Demospongiae -- horn
sponges -- This class has the greatest number of sponge
species and includes the familiar household varieties as
well as brilliantly colored fans, vases or spreading
branches.
Class Hexactinellida -- glass sponges
-- Skeletons composed of six-pointed bits of silica that
in many species are formed into elaborate lattices like
those of the Venus' flower-basket.
Class
Calcarea -- All these sponges are small, with
skeletons of calcium carbonate. Some are vase-shaped;
others are irregular.